U.S. patent number 4,362,861 [Application Number 06/311,386] was granted by the patent office on 1982-12-07 for polyesterimide.
This patent grant is currently assigned to Schenectady Chemicals, Inc.. Invention is credited to Dennis C. Shen.
United States Patent |
4,362,861 |
Shen |
December 7, 1982 |
Polyesterimide
Abstract
A low molecular weight polyester-imide resin is prepared wherein
there is employed as the dibasic acid either 100% of the diimide
dicarboxylic prepared by reacting two moles of trimellitic
anhydride with one mole of methylene dianiline (the diimide is
abbreviated DID) or oxydianiline or the dibasic acid can also
contain a small percent of another aromatic acid. The product is
used to produce coated wires having outstanding heat shock. The
product also is useful to provide a top coat to wire coated with a
polyester or with another polyester-imide.
Inventors: |
Shen; Dennis C. (Clifton Park,
NY) |
Assignee: |
Schenectady Chemicals, Inc.
(Schenectady, NY)
|
Family
ID: |
26914618 |
Appl.
No.: |
06/311,386 |
Filed: |
October 14, 1981 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
220160 |
Dec 23, 1980 |
|
|
|
|
Current U.S.
Class: |
528/289; 428/379;
428/383; 428/458; 428/473.5; 528/350 |
Current CPC
Class: |
C08G
73/16 (20130101); H01B 3/306 (20130101); H01B
3/308 (20130101); Y10T 428/294 (20150115); Y10T
428/31721 (20150401); Y10T 428/2947 (20150115); Y10T
428/31681 (20150401) |
Current International
Class: |
C08G
73/00 (20060101); C08G 73/16 (20060101); H01B
3/30 (20060101); C08G 073/16 () |
Field of
Search: |
;528/288,289,350
;428/379,383,458,473.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Griffin; Ronald W.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Parent Case Text
REFERENCE TO THE RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
220,160, filed Dec. 23, 1980 and now abandoned.
Claims
What is claimed is:
1. A polyester-imide having a hydroxy to carboxy equivalent ratio
of 2.65:1 to 3.67:1, a trihydric alcohol to dihydric alcohol molar
ratio of 0.23:1 to 0.62:1, the polyester-imide containing 40 to 50
equivalent % of imide groups, the imide groups being from the imide
dibasic acid of the formula ##STR2## the polyester having been made
with the following mole percentages of ingredients:
wherein the dihydric alcohol is ethylene glycol, the trihydric
alcohol is tris(2-hydroxyethyl) isocyanurate, the aromatic diamine
is methylene dianiline, the mole ratio of trimellitic anhydride to
methylene dianiline is about 2:1, the aromatic diacid is
terephthalic acid and the aromatic diester is a di(lower alkyl)
terephthalate, the polyester-imide has a molecular weight of 700 to
2000, the hydroxyl number of the polyester-imide is 350 to 450,
said polyester-imide being capable of forming a single coat
insulating coating on an electrical wire capable of withstanding
heat shock at 260.degree. C.
2. A polyester-imide according to claim 1 wherein there is employed
terephthalic acid.
3. A polyester-imide according to claim 1 wherein the aromatic
diacid or diester content is 0.
4. A polyester-imide according to claim 1 wherein the aromatic
diacid or diester content is 2-7 mole %.
5. A polyester-imide according to claim 1 having a molecular weight
of 750-1050.
6. A polyester-imide according to claim 1 having a hydroxy to
carboxyl equivalent ratio of 2.65:1 to 3.33:1, a trihydric alcohol
to dihydric alcohol molar ratio of 0.4:1 to 0.5:1 and the
polyester-imide contains 42.5-50 equivalent % of imide groups.
7. A polyester-imide according to claim 6 wherein the
polyester-imide contains 45-50 equivalent % of imide groups.
8. A process of preparing the polyesterimide of claim 1 comprising
heating (1) the dihydric alcohol, trihydric alcohol, aromatic
diamine and trimellitic anhydride or (2) the dihydric alcohol,
trihydric alcohol, aromatic diamine, trimellitic anhydride and the
aromatic diacid or diester in an organic solvent until the
polyester-imide is formed.
9. A process of preparing the polyesterimide of claim 1 comprising
heating (1) the dihydric alcohol, trihydric alcohol or (2) the
dihydric alcohol, trihydric alcohol, performed imide dibasic acid
and aromatic diacid or diester in an organic solvent until the
polyester-imide is formed.
10. An electrical conductor having an insulating coating prepared
by curing the polyesterimide of claim 1 thereon.
11. An electrical conductor according to claim 10 wherein the
conductor is in the form of wire.
12. An electrical conductor in wire form having an insulating
coating prepared by curing the polyester-imide of claim 2
thereon.
13. An electrical conductor in wire form having an insulating
coating prepared by curing the polyester-imide of claim 3
thereon.
14. An electrical conductor in wire form having an insulating
coating prepared by curing the polyester-imide of claim 4
thereon.
15. An electrical conductor in wire form having an insulating
coating prepared by curing the polyester-imide of claim 5
thereon.
16. An electrical conductor in wire form having an insulating
coating prepared by curing the polyester-imide of claim 6
thereon.
17. An electrical conductor in wire form having an insulating
coating prepared by curing the polyester-imide of claim 7
thereon.
18. A coating composition containing the polyester-imide of claim 1
dissolved in an organic solvent.
19. A coating composition according to claim 18 free from
water.
20. A coating composition comprising an aqueous solvent and the
reaction product of the polyester-imide of claim 1 with sufficient
amount of a tertiary amine to render the reaction product soluble
in the aqueous solvent mixture.
21. A coating composition according to claim 20 having a pH of 7 to
9.
22. A coating composition according to claim 21 wherein the pH is
7.5 to 8.5.
23. A process of preparing an insulated electrical conductor wire
comprising applying to the wire the coating composition of claim 21
and curing the polyester-imide on the wire.
24. The insulated wire produced by the process of claim 23.
25. The process of preparing an insulated electrical conductor wire
comprising applying to the wire the coating composition of claim 20
and curing the polyester-imide on the wire.
26. The insulated wire prepared by the process of claim 25.
27. The process of preparing an insulated electrical conductor wire
comprising applying to the wire the coating composition of claim 19
and curing the polyester-imide on the wire.
28. The insulated wire prepared by the process of claim 27.
29. The polyester-imide according to claim 1 having a molecular
weight of 700-1300.
30. A polyester-imide having a hydroxy to carboxy equivalent ratio
of 2.65:1 to 4.0:1, a trihydric alcohol to dihydric alcohol molar
ratio of 0.23:1 to 0.62:1, the polyester-imide containing 40 to 50
equivalent % of imide groups, the imide groups being from the imide
dibasic acid of the formula ##STR3## where X is O or CH.sub.2, the
polyester having been made with the following mole percentages of
ingredients:
wherein the dihydric alcohol is ethylene glycol or a mixture of
ethylene glycol and a minor amount of another alkanediol, the
trihydric alcohol is tris(2-hydroxyethyl) isocyanurate, the
aromatic diamine is methylene dianiline or oxydianiline, the mole
ratio of trimellitic anhydride to methylene dianiline or
oxydianiline is about 2:1, the aromatic diacid is terephthalic acid
and the aromatic diester is a di(lower alkyl) terephthalate, the
polyester-imide has a molecular weight of 700 to 2000, the hydroxyl
number of the polyester-imide is 350 to 450, said polyester-imide
being capable of forming a single coat insulating coating on an
electrical wire capable of withstanding heat shock at 260.degree.
C.
31. A polyester-imide according to claim 30 wherein the aromatic
diamine is oxydianiline and the hydroxy to carboxy equivalent ratio
is 2.65:1 to 3.67:1.
32. An electrical conductor having an insulating top coat prepared
by curing the polyester-imide of claim 30 thereon and a base coat
of a polyester or a different polyester-imide.
33. An electrical conductor according to claim 32 wherein the base
coat is a polyester.
34. An electrical conductor according to claim 33 wherein the
polyester is a tris(2-hydroxyethyl) isocyanurateethylene glycol
terephthalate polymer.
35. An electrical conductor according to claim 33 wherein the
conductor is in the form of a wire.
36. An electrical conductor according to claim 32 wherein the
conductor is in the form of a wire.
37. An electrical conductor having an insulating top coat prepared
by curing the polyester-imide of claim 1 thereon and a base coat of
a polyester or a different polyester-imide.
38. An electrical conductor according to claim 37 wherein the base
coat is a polyester.
39. An electrical conductor according to claim 38 wherein the
polyester is a tris(2-hydroxyethyl) isocyanurateethylene glycol
terephthalate polymer.
40. An electrical conductor according to claim 38 wherein the
conductor is in the form of a wire.
41. An electrical conductor according to claim 37 wherein the
conductor is in the form of a wire.
42. An electrical conductor according to claim 41 wherein there is
employed terephthalic acid as a component of the polyester-imide
having an equivalent ratio of 2.65:1 to 3.67:1.
43. An electrical conductor according to claim 41 wherein said
aromatic diacid or diester content is 0.
44. An electrical conductor according to claim 41 wherein said
aromatic diacid or diester content is 2-7 mole %.
45. An electrical conductor according to claim 41 wherein the
molecular weight of the polyester-imide having an equivalent ratio
of 2.65:1 to 3.67:1 is 750-1050.
46. An electrical conductor according to claim 41 wherein the
polyester-imide has a hydroxy to carboxyl equivalent ratio of
2.65:1 to 3.33:1, a trihydric alcohol to dihydric alcohol molar
ratio of 0.4:1 to 0.5:1 and the polyester-imide contains 42.5-50
equivalent % of imide groups.
47. An electrical conductor according to claim 46 wherein the
polyester-imide contains 45-50 equivalent % of imide groups.
48. A process of preparing an insulated electrical conductor wire
comprising applying to the wire a base coat of a polyester or a
polyester-imide and there applying a top coat of the
polyester-imide of claim 30, the polyester-imide of the base coat
being different from that of the top coat.
49. A process of preparing an insulated electrical conductor wire
comprising applying to the wire a base coat of a polyester or a
polyester-imide and there applying a top coat of the
polyester-imide of claim 1, the polyester-imide of the base coat
being different from that of the top coat.
50. An electrical conductor according to claim 10 wherein the
coating also contains a phenol-formaldehyde or cresol-formaldehyde
resin.
51. An electrical conductor according to claim 50 wherein the
coating contains a m,p-cresol-formaldehyde resin.
52. A coating composition according to claim 18 including a
phenol-formaldehyde or cresol-formaldehyde resin.
53. A coating composition according to claim 32 including a
m,p-cresol-formaldehyde resin.
54. A coating composition according to claim 20 including a
phenol-formaldehyde or cresol-formaldehyde resin.
55. A coating composition according to claim 54 including a
m,p-cresol-formaldehyde resin.
56. A process according to claim 25 wherein the coating composition
includes a phenol-formaldehyde or cresol-formaldehyde resin.
57. The insulated wire produced by the process of claim 56.
58. A process according to claim 56 wherein the coating composition
includes a m,p-cresol-formaldehyde resin.
59. The insulated wire produced by the process of claim 58.
60. A process according to claim 27 wherein the coating composition
includes a phenol-formaldehyde or cresol-formaldehyde resin.
61. The insulated wire produced by the process of claim 60.
62. In an electrical conductor having an insulating coating
comprising a polyesterimide the improvement of employing as the
polyesterimide the product obtained by curing the polyesterimide of
claim 1 on said electrical conductor.
63. In a coating composition containing a polyester-imide dissolved
in an organic solvent the improvement comprising employing as the
polyester-imide the polyester-imide of claim 1.
64. In a coating composition comprising an aqueous solvent and a
polyester-imide the improvement comprising employing as the
polyester-imide the reaction product of the polyester-imide of
claim 1 with sufficient amount of a tertiary amine to render the
reaction product soluble in the aqueous solvent mixture.
65. An electrical conductor according to claim 32 wherein the
coating also contains a phenol-formaldehyde or cresol-formaldehyde
resin.
66. An electrical conductor according to claim 65 wherein the
coating contains a m,p-cresol-formaldehyde resin.
67. An electrical conductor according to claim 33 wherein the top
coat also contains a phenol-formaldehyde or cresol-formaldehyde
resin.
68. An electrical conductor according to claim 34 wherein the top
coat also contains a phenol-formaldehyde or cresol-formaldehyde
resin.
69. A process according to claim 48 wherein the top coating
composition includes a phenol-formaldehyde or cresol-formaldehyde
resin.
70. The insulated wire produced by the process of claim 69.
71. A process according to claim 69 wherein the coating composition
includes a m,p-cresol-formaldehyde resin.
72. The insulated wire produced by the process of claim 71.
73. A process according to claim 49 wherein the coating composition
includes a phenol-formaldehyde or cresol-formaldehyde resin.
74. The insulated wire produced by the process of claim 73.
75. In an electrical conductor having an insulating coating
comprising a polyesterimide the improvement of employing as the
polyesterimide the product obtained by curing the polyesterimide of
claim 30 on said electrical conductor.
76. In a coating composition containing a polyester-imide dissolved
in an organic solvent the improvement comprising employing as the
polyester-imide the polyester-imide of claim 30.
77. In a coating composition comprising an aqueous solvent and a
polyester-imide the improvement comprising employing as the
polyester-imide the reaction product of the polyester-imide of
claim 30 with sufficient amount of a tertiary amine to render the
reaction product soluble in the aqueous solvent mixture.
Description
BACKGROUND OF THE INVENTION
The present invention relates to the preparation of novel
polyester-imides and their use in coating wires with outstanding
physical properties.
In Schmidt U.S. Pat. No. 3,697,471, there is disclosed in Example 9
a polyester-imide prepared from ethylene glycol, glycerine and a
diimide dicarboxylic acid prepared by reacting two moles of
trimellitic anhydride with one mole of methylene dianiline. This
diimide dicarboxylic acid is sometimes abbreviated hereinafter as
DID. The polymers prepared in Schmidt have a triol to diol molar
ratio of 0.676, a hydroxy to carboxy equivalent ratio of 1.41. The
product has a 250.degree. C. heat shock without using prestretch of
the wire and employing one hour of baking.
The commercial material made under the Schmidt patent known as
Terebec FH contains substantial amounts of ester derived from
terephthalic acid and a small amount of imide derived from DID.
Terebec FH in inferior in properties to the commercial
polyester-imide, ISOMID, made in accordance with Meyer U.S. Pat.
No. 3,426,098. Thus, in regard to heat shock precent passing
one-half hour at 200.degree. C. using 20 percent prestretch, the
following results are noted.
______________________________________ Mandrel Size Terebec FH
ISOMID ______________________________________ 1X 30 0 2X 50 80 3X
60 100 4X 90 100 ______________________________________
When ISOMID was tested at 260.degree. C., the results in the same
Mandrel Sizes was 0-0-0-0.
It has previously been proposed to use polyesterimide resins as a
top coat for electrical conductors coated with a polyester resin or
other resin, e.g., Ishizuka U.S. Pat. No. 4,208,464, Keske U.S.
Pat. No. 4,070,524, Czajka U.S. Pat. No. 3,944,706, Keske U.S. Pat.
No. 4,012,555, and Keske U.S. Pat. No. 4,012,556. However, the
products of these patents do not have sufficiently good heat shock
properties. In fact, a number of these patents, e.g., the Keske and
Czajka patents, are directed to self-bonding coatings for magnet
wires. The self-bonding property is incompatible with good heat
shock properties. Ishizuka prepares a water soluble polyester-imide
having an acid value of 30-50, an OH/COOH equivalent ratio of 1:1
to 2:1 and requires a substantial amount of an aliphatic
polycarboxylic acid.
SUMMARY OF THE INVENTION
It has now been found that there can be prepared a polyester-imide
having outstanding physical properties when applied to a wire.
Thus, it is capable of withstanding heat shock at 260.degree. C.
compared to the 200.degree. C. of the commercial ISOMID referred to
above. The new polyester-imide can compete, as a single-coat
system, against the amide-imide topcoated polyester (e.g.,
amide-imide coated ISONEL 200/ system now used in the art). The new
polyester-imide passes the A. O. Smith blister test and had good
burn-out results.
The new polyester-imide employs as the dicarboxylic acid DID or a
mixture of DID with a small amount of another aromatic dicarboxylic
acid.
The parameters of the invention are as follows:
(1) A polyester-imide is made with a hydroxyl to carboxyl
equivalent ratio of 2.65:1 to 3.67:1, preferably 2.65:1 to 3.33:1.
The ratio can even be as high as 4.0:1.
(2) A polyester-imide is made with trihydric alcohol to dihydric
alcohol molar ratio of 0.23:1 to 0.62:1, preferably 0.4:1 to
0.5:1.
(3) The polyester-imide is made with 40-50%, usually 42.5-50%, by
equivalent, imide groups, preferably 45-50%, by equivalent, imide
groups.
(4) The polyester-imide is made with the following mole percentages
of ingredients:
______________________________________ Mole %
______________________________________ Dihydric alcohol 29-56
Trihydric alcohol 9-19 Aromatic Diamine 11-18 Trimellitic Anhydride
22-35 Aromatic Diacid or Diester 0-7
______________________________________
It should be noted that the molar ratios of the reactants change
quite considerably depending on whether one starts with trimellitic
anhydride and methylene dianiline on the one hand or prereacts them
and then bases the calculation on the preformed DID. Two moles of
TMA and one mole of MDA are condensed to become only one mole of
DID, thereby changing the molar calculation. In Example 12 for
instance, the mole percent of THEIC is 23% based on the use of DID,
or 15.3% when the MDA and TMA are not prereacted to form DID. THEIC
molar percentages are always higher in those cases using prereacted
DID, because the DID always involve a fewer number of total moles
and therefore the contribution of the THEIC becomes proportionately
greater.
The mole ratios in parameter (4) and in the claims are calculated
on a basis that TMA and the diamine are present rather than
preformed DID.
(5) The polyester-imide normally has an average molecular weight of
from 700 to 1300 or even up to 2,000, but preferably an average
molecular weight of from 750-1050. The molecular weights were
determined by Vapor Pressure Osmometer.
(6) The hydroxyl number of the polyester-imide frequently is within
380-420, but this can be varied, e.g., it can be as low as 350 or
as high as 450.
(7) The polyester-imide is made using (1) tris (2-hydroxyethyl)
isocyanurate (THEIC), (2) a dibasic acid such as terephthalic acid
(TA) or its lower alkyl esters, e.g., dimethyl terephthalate (DMT),
diethyl terephthalate or dibutyl terephthalate, (3) trimellitic
anhydride (TMA), (4) a diamine, such as methylene dianiline or
oxydianiline, preferably methylene dianiline and (5) a dihydric
alcohol such as ethylene glycol.
(8) The polyester-imides of this invention can be cooked at 70-100%
concentration in various kinds of solvent media, such as cresylic
acid, n-methyl pyrrolidone, ethylene glycol, methyl Carbitol
(monomethyl ether of diethylene glycol) or a mixture of 50%
cresylic acid and 50% ethylene glycol.
(9) The polyester-imide resins of the invention are soluble in a
wide variety of solvents including phenol, cresol or cresylic acid
or other phenols or mixtures of phenols. They are preferably
dissolved in a mixture of solvent containing 29-59% of cresylic
Acid 43 (Merichem Co.), 12-19% of phenol, 17-38% of Solvesso 100 (a
mixture of tetramethyl benzene with dialkyl- and trialkyl-benzene
boiling in the range 182.degree.-204.degree. C.) or Solvesso 150 (a
blend of 70% Solvesso 100 and 30% heavy aromatic naphtha). The
solvent can be a mixture of 0-60% water, 0-28% n-methyl
pyrrolidone, 0-17% ethylene glycol and 12-89% methyl Carbitol. To
solubilize these polyester-imides in water, various amines may be
employed that react with the free carboxylic groups or amic acid
groups available to form the salts that are soluble in water. These
amines may be of the alkyl and alkanolamines such as
trimethylamine, triethylamine, triethanolamine,
dimethylethanolamine, methyldiethanolamine. A sufficient quantity
of amine is employed to raise the pH of the aqueous solution to a
range of 7-9 and preferably 7.5-8.5.
There can be added to the wire enamels of the invention
conventional modifiers such as Tyzor TPT (tetraisopropyltitanate),
TBT (tetrabutyltitanate), tetraphenyltitanate, tetracresyltitanate,
etc., as well as polyisocyanates, such as Mondur SH which is the
cyclic trimer of 2,4 and 2,6-tolylene diisocyanates having the
three free isocyanate groups blocked by phenol, or alternately any
of the other polyisocyanates mentioned in Meyer U.S. Pat. No.
3,426,098, or cresol, or metal driers, e.g., cobalt naphthenate,
manganese naphthenate, calcium naphthenate, zinc octoate and
Polycat 200. There can be used other titanate and driers, e.g., any
of those mentioned in Keating U.S. Pat. No. 4,119,608. Also there
can be added to the enamel phenolic resins such as
phenol-formaldehyde cresol-formaldehyde resins.
The wire enamels can be applied to copper, aluminum, silver or
other wires using conventional coating procedures and wire speeds,
e.g., 30-60 ft./min. and curing the wire is carried out at
conventional temperatures, e.g., 260.degree. C. to 482.degree. C.,
usually 260.degree.-427.degree. C.
The polyester-imide of the invention also has been found useful to
provide a topcoat for wires base coated with a polyester resin or
another polyester-imide resin to provide a coated wire having good
heat shock properties. Moreover, the present polyester-imides
provide this improved heat shock coated wires at lower cost than
using a conventional amide-imide polymer top coat (the normal
procedure is to apply 4 coats of polyester base coat (e.g., Isonel
200 prepared from tris(2-hydroxyethyl) isocyanurate, ethylene
glycol and terephthalic acid) followed by 2 coats of the
amide-imide polymer using N-methyl pyrrolidone as a solvent.
Instead of using the amide-imide polymer when there is employed the
polyester-imide enamel of the present invention as a topcoat (using
1 or 2 coats of the polyester-imide) for polyester (or a different
polyester-imide) coated wire, there can be avoided the need for
N-methyl pyrrolidone as a solvent. Lower cost solvents can be
employed. Also, the enamel can be operated at higher solids
content, e.g. 40%, so that less solvent goes up the stack.
The high temperature basecoats can be conventional polyesters, for
example those set forth in Meyer U.S. Pat. No. 3,342,780 or
convention polyester-imide resins, for example those in Meyer U.S.
Pat. No. 3,426,098. The entire disclosures of both Meyer patents is
hereby incorporated by reference and relied upon. Illustrative of
the polyester resins are the reaction products of
tris(2-hydroxyethyl) isocyanurate (THEIC), ethylene glycol and
terephthalic acid or isophthalic acid. For Class F enamels, the
THEIC in the base coat can be replaced by glycerine,
trimethylolpropane or trimethylolethane.
Illustrative of a polyester-imide resin base coat is the reaction
product of THEIC, ethylene glycol, terephthalic acid (or
isophthalic acid), methylene dianiline (or oxydianiline) and
trimellitic anhydride. In place of THEIC, there can be used
glycerine, e.g. as in the polyester-imides of Schmidt U.S. Pat. No.
3,697,471, the entire disclosure of which is hereby incorporated by
reference and relied upon. Likewise, there can be used as the base
coat the diethylene glycol or triethylene glycol monoether modified
polyester-imide resins of Keating U.S. Pat. No. 4,119,608, the
entire disclosure of which is hereby incorporated by reference.
The polyester-imide consists essentially of or consists of the
stated materials.
The composition can comprise, consist essentially of, or consist of
the materials set forth.
Unless otherwise indicated, all parts and percentages are by
weight.
The following abbreviations are used in the examples:
EG=ethylene glycol
TA=terephthalic acid
DMT=dimethyl terephthalate
TMA=trimellitic anhydride
THEIC=tris-(2-hydroxyethyl) isocyanurate
MDA=methylene dianiline
NMP=N-methyl pyrrolidone
TPT=tetraisopropyltitanate
DID=diimide diacid (adduct of 1 mol of MDA and 2 moles of TMA)
Tyzor TE=triethanolamine titanium chelate
It has been found critical to use the stated materials. Thus,
replacing THEIC by trimethylol propane or glycerine does not give
as good results nor does replacing terephthalic acid by isophthalic
acid or adipic acid as the other acid when less than 100% DID is
used as the acid component. Likewise, replacing ethylene glycol
with propylene glycol or 1,4-butanediol does not give as good
results nor does including 1,2,3,4-butane tetracarboxylic anhydride
as part of the acid. While it is preferable to employ ethylene
glycol as the sole dihydric alcohol, it is possible to replace a
minor portion of the ethylene glycol by another dihydric alcohol,
e.g., an alkanediol, such as 1,4-butylene glycol. For example,
there can be used an ethylene glycol-butylene glycol ratio of
75:25.
The imide content of the polyester-imide is expressed by
EXAMPLE 1
(a) Preparation of Polymer
______________________________________ Weight Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 321.9 -- -- (B) EG 230.7 3.72 33.7 (C) THEIC 440.8 1.69
15.3 (D) TMA 721.0 3.76 34.0 (E) MDA 371.9 1.88 17.0
______________________________________
The polyester-imide was made with hydroxyl/carboxyl ratio of
3.33/1, triol/diol molar ratio of 0.45/1 and 50% imide
content(equivalent). Materials A, B, C, D and E were charged into a
3-liter, three-necked flask equipped with an agitator driven by an
electronically-controlled motor, thermometer for flask, 3-bubble
Snyder fractionating column and water-cooled condenser. The
temperature was increased gradually to 220.degree.-230.degree. C.
and held there until the desired physicals were attained. At a
viscosity of X (Gardner-Holdt) as measured at 38% solids in
cresylic acid the reaction was terminated, and the melt discharged
into a pan to solidify. The solids of the resin were 86.7%,
Molecular Weight of the polymer 987.
(b) Preparation of Wire Enamel
______________________________________ Weight, Grams
______________________________________ (A) The polyester-imide
prepared 369.1 in Example (1a) (B) CA-43 120.7 (C) Phenol 90.5 (D)
Solvesso 100 172.4 (E) Phenolic Resin (m, p Cresol-formaldehyde
36.6 resin-% by weight dissolved in CA-43) (F) TPT 12.2 (G) Blocked
Isocyanate (Mondur SH-% by weight 70.4 dissolved in CA-43 and
Solvesso 100) (H) Ethylene Glycol 17.0
______________________________________
A solution of the polymer 1(a) was made by dissolving the resin in
(B), (C) and (D) and holding the mixture at 120.degree. C. with
agitation until it was dissolved. The solution was cooled to
88.degree. C. and (E), (F) and (G) were added. The solution was
then heated to 120.degree. C. and held for two hours. The viscosity
of the resulting wire enamel was a V 3/4 and the solids were
determined to be 39.2%.
(c) Preparation of Wire Enamel
______________________________________ Weight, Grams
______________________________________ (A) The polyester-imide
262.4 prepared in Example 1(a) (B) CA-43 247.0 (C) Phenol 109.8 (D)
Solvesso 150 82.3 (E) Solvesso 100 109.8 (F) Phenolic Resin 29.6
(G) TPT 10.0 (H) Blocked Isocyanate 63.1
______________________________________
The wire enamel was made by using the same procedure as described
in Example 1(b) except the increased amounts of additives (F), (G)
and (H) and 82.3 grams of Solvesso 150 were used in this
formulation. The viscosity of this enamel was an E and the solids
were determined to be 28.4%.
(d) Preparation of Wire Enamel
______________________________________ Weight, Grams
______________________________________ (A) The polyester-imide
262.4 prepared in Example 1(a) (B) CA-43 238.8 (C) Phenol 106.1 (D)
Solvesso 150 79.6 (E) Solvesso 100 106.1 (F) Phenolic Resin 17.4
(G) TPT 6.4 (H) Blocked Isocyanate 40.3
______________________________________
The wire enamel was made by using the same procedure as described
in Example 1(b). The viscosity of this enamel was a D 3/4 and the
solids were determined to be 28.3%.
EXAMPLE 2
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 330.2 -- -- (B) EG 232.5 3.75 35.4 (C) THEIC 440.6 1.69
16.0 (D) TMA 657.6 3.43 32.4 (E) MDA 339.1 1.71 16.2
______________________________________
The polyester-imide was made with imide content of 50 eq. % and a
hydroxyl/carboxyl ratio of 3.67. The same procedure was used as
described in Example 1(a). After a viscosity of U 1/2 was attained,
the resin was discharged into a pan to solidify. The solids were
determined to be 82.7%. The molecular weight of the polymer was
1082.
(b) Preparation of Wire Enamel
Polyester-imide 2(a), 386.8 grams, was used in place of 369.1 grams
of polyester-imide 1(a) and the same procedure followed as in
Example 1(b). The viscosity of the resulting wire enamel was a U
and the solids were determined to be 40.3%.
EXAMPLE 3
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 358.7 -- -- (B) EG 319.7 5.16 41.0 (C) THEIC 309.3 1.19
9.4 (D) TMA 799.8 4.17 33.1 (E) MDA 412.4 2.08 16.5
______________________________________
This polyester-imide with triol/diol molar ratio of 0.23/1 and
imide content of 50 eq. % was made by using the same procedure as
described in Example 1(a). A viscosity of U 1/2 and 79.6% solids
were obtained for this polymer. The molecular weight of the polymer
was 1290.
(b) Preparation of Wire Enamel
Polyester-imide 3(a), 401.6 grams, was used in place of 369.1 grams
of polyester-imide 1(a) and the same procedure followed as in
Example 1(b). The viscosity of the resulting wire enamel was a U
1/2 and the solids were determined to be 40.2%.
EXAMPLE 4
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 394.8 -- -- (B) EG 286.0 4.61 34.9 (C) THEIC 542.1 2.08
15.7 (D) TMA 806.4 4.20 31.8 (E) MDA 415.8 2.10 15.9 (F) TA 36.5
0.22 1.7 ______________________________________
This polyester-imide with 47.5 equivalent % imide content was made
by using the same procedure as described in Example 1(a). This
polymer had a viscosity of V and a solids of 86.0%. The molecular
weight was 1541.
(b) Preparation of Wire Enamel
The wire enamel solution was made by using the same procedure as
described in Example 1(b) except with 371.7 grams of
polyester-imide 4(a) in place of 369.1 grams of polyester-imide
1(a). This enamel had a viscosity of T 3/4 and a solids of
38.8%.
EXAMPLE 5
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 321.9 -- -- (B) EG 251.7 4.06 36.0 (C) THEIC 475.1 1.82
16.2 (D) TMA 641.3 3.34 29.7 (E) MDA 330.7 1.67 14.8 (F) TA 61.0
0.37 3.3 ______________________________________
This polyester-imide with 45 equivalent percent imide content was
made by using the same procedure as outlined in Example 1(a) and
the final polymer had a viscosity of V 1/4 and a solids of
85.5%.
(b) Preparation of Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b). The viscosity of T 3/4 and solids of 39.4% were
obtained for this wire enamel.
EXAMPLE 6
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 347.9 -- -- (B) EG 278.9 4.50 32.1 (C) THEIC 529.1 2.03
14.5 (D) TMA 894.7 4.66 33.2 (E) MDA 461.3 2.33 16.6 (F) TA 85.0
0.51 3.6 ______________________________________
This polyester-imide with 45 equivalent % imide content and OH/COOH
ratio of 2.65 was prepared by using the same equipment and
procedure as outlined in Example 1(a). It was controlled to a final
viscosity of X and a solids of 88.0%.
(b) Preparation of Wire Enamel
The wire enamel was made by using the same procedure as outlined in
Example 1(b) except 363.3 grams of polyester-imide 6(a) were used
in place of 369.1 grams of the polymer 1(a). A viscosity of V and a
solids of 40.0% were obtained for this enamel.
EXAMPLE 7
(a) Preparation of Polymer
______________________________________ Weight Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 149.3 -- -- (B) EG 184.8 2.98 40.6 (C) THEIC 222.4 0.852
11.6 (D) TMA 384.0 2.0 27.3 (E) MDA 198.0 1.0 13.6 (F) TA 83.0 0.5
6.8 ______________________________________
This polyester-imide with 40 equivalent % imide content, OH/COOH
ratio of 2.84 and triol/diol molar ratio of 0.29 was prepared by
employing the same equipment and procedure as outlined in Example
1(a). It was controlled to a final viscosity of U 1/2 and solids of
82.6%. The molecular weight of the polymer was 773.
(b) Preparation of Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except with 387 grams of polyester-imide 7(a) in
place of 369.1 grams of polyester-imide 1(a). A viscosity of U 1/4
and solids of 40.0% were obtained for this enamel.
EXAMPLE 8
(a) Preparation of Polymer
The same equipment and procedure as outlined in Example 1(a) was
employed in preparing this polymer except n-methyl pyrrolidone was
used in place of cresylic acid as solvent medium. It was reacted to
a viscosity of W at 38% solids in cresylic acid and a solids of
82.5%.
(b) Preparation of Conventional Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except 364.5 grams of the polymer 8(a) was used in
place of 369.1 grams of the polymer 1(a). A viscosity of X 1/2 and
a solids of 40.3% were obtained for this wire enamel.
(c) Preparation of Aqueous Wire Enamels
The hard resin 8(a) was then fractured into small chunks, and 472.7
grams of the polymer along with 39.1 grams of methyl Carbitol was
charged to a 3-liter, three-necked round-bottom flask, and heated
to 132.degree. C. until the polymer was fluid and dissolved. At a
temperature of 120.degree. C., 46.8 grams of dimethylethanolamine
(DMEA) was added to the flask. Then the batch was cooled to
105.degree. C., 182.1 grams of distilled water was added to the
flask. Additional water, amine and solvent were added to reduce the
viscosity. Then on a solids-to-solids basis 5.5% Tyzor TE was added
to the solution to make the final enamel having a viscosity of X
1/4, a pH of 8 and a solids of 47.6%.
EXAMPLE 9
(a) Preparation of Polymer
The same equipment and procedure as outlined in Example 1(a) was
employed in preparing this polymer except methyl Carbitol was used
in place of cresylic acid as solvent medium. It was reacted to a
viscosity of V 1/4 at 38% in cresylic acid and a solids of
80.9%.
(b) Preparation of Conventional Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except 395.4 grams of the polymer 9(a) was used in
place of 369.1 grams of the polymer 1(a). A viscosity of T 1/2 and
a solids of 40.7% were obtained for this enamel.
(c) Preparation of Aqueous Wire Enamel
Using the same equipment and procedure as described in 8(c) an
aqueous enamel was prepared by blending 481.9 grams of base polymer
9(a) with 29.9 grams of methyl Carbitol, 66.8 grams of DMEA, 182.6
grams of distilled water and 21.9 grams of Tyzor TE to provide an
enamel having the following properties: viscosity=X 1/2, pH=7.5, %
solids=53.0%.
EXAMPLE 10
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) EG 552.6 8.91 54.9 (B) THEIC 440.8 1.69 10.4 (C) TMA 721.0 3.76
23.2 (D) MDA 371.9 1.88 11.6
______________________________________
The same equipment and procedure as outlined in Example 1(a) was
employed in preparing this polymer except ethylene glycol was used
in place of cresylic acid as solvent medium. It was reacted to a
viscosity of X 3/4 at 38% solids in cresylic acid and a solids of
88.7%.
(b) Preparation of Conventional Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except 360.8 grams of the polymer 10(a) was used in
place of 369.1 grams of the polymer 1(a). A viscosity of T and a
solids of 41% were obtained for this enamel.
(c) Preparation of Aqueous Wire Enamel
Using the same equipment and procedure as described in 8(c) an
aqueous enamel was prepared by blending 439.7 grams of polymer
10(a), 72.1 grams of methyl Carbitol, 66.8 grams of DMEA, 182.6
grams of distilled water and 21.9 grams of Tyzor TE to provide an
enamel having the following properties: viscosity=Y, pH=7.5, and %
solids=48.6%.
EXAMPLE 11
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 318.4 -- -- (B) EG 249.0 4.02 36.1 (C) THEIC 471.8 1.81
16.2 (D) TMA 634.5 3.30 29.6 (E) MDA 327.3 1.65 14.8 (F) DMT 71.4
0.368 3.3 (G) Xylol ______________________________________
This same equipment and procedure as outlined in Example 5(a) was
employed in preparing this polymer except 61 grams of TA were
replaced by 71.4 grams of DMT. It was controlled to a viscosity of
U 1/4 at 38% in cresylic acid and a solids of 81.6%. The molecular
weight of the polymer was 1481.
(b) Preparation of Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except 391.8 grams of the polymer 11(a) were used
in place of 369.1 grams of the polymer 1(a). A viscosity of U 1/2
and a solids of 40.5% were obtained for this enamel.
EXAMPLE 12
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 63.8 -- -- (B) EG 45.7 0.737 51.1 (C) THEIC 87.3 0.334
23.1 (D) DID 203.2 0.372 25.8
______________________________________
The same equipment and procedure as outlined in Example 1(a) was
employed in preparing this polymer except DID was used in place of
TMA and MDA. It was reacted to a viscosity of U 3/4 at 38% in
cresylic acid and a solids of 84.8%. The molecular weight of the
polymer was 1967.
(b) Preparation of Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except 377.4 grams of the polymer 12(a) were used
in place of 369.1 grams of the polymer 1(a). A viscosity of U 3/4
and a solids of 39.2% were obtained for this enamel.
EXAMPLE 13
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 321.9 -- -- (B) EG 230.7 3.72 33.7 (C) THEIC 440.8 1.69
15.3 (D) TMA 721.0 3.76 34.0 (E) MDA 371.9 1.88 17.0 (F) Cobalt 24
ppm* Naphthenate (G) Calcium 96 ppm* Naphthenate (H) Manganese 72
ppm* Naphthenate ______________________________________ *Based on
total solids of the batch
The same equipment and procedure as outlined in Example 1(a) was
employed in preparing this polymer except metal driers, (F), (G)
and (H) were added. It was reacted to a viscosity of X 1/4 at 38%
solids in cresylic acid and a solids of 86.1%.
(b) Preparation of Wire Enamel
The wire enamel was made by using the same procedure as described
in Example 1(b) except 371.7 grams of polymer 13(a) were used to
replace 369.1 grams of polymer 1(a). A viscosity of V 1/2 and a
solids of 41.4% were obtained for this enamel.
EXAMPLE 14
(a) Preparation of Polymer
______________________________________ Weight, Mol % of Reactants
Grams Mols Total Reactants ______________________________________
(A) CA-43 321.9 -- -- (B) EG 573.2 9.25 55.8 (C) THEIC 440.8 1.69
10.2 (D) TMA 721.0 3.76 22.7 (E) MDA 371.9 1.88 11.3
______________________________________
The same equipment and procedure as outlined in Example 1(a) was
employed in preparing this polymer except 342.5 grams of excess
ethylene glycol was used in this formulation. It was controlled to
a final viscosity of U 3/4 and a solids of 82.6%.
(b) Preparation of Wire Enamel
The wire enamel was prepared by using the same procedure as
described in Example 1(b) except 387.4 grams of the polymer 14(a)
was used to replace 369.1 grams of the polymer 1(a). A viscosity of
U and a solids of 41.6% were obtained for this enamel.
The percent solids of the base polymer and wire enamel solutions
were determined using two-gram samples in a forced-air oven held at
200.degree. C. for two hours.
After applying the enamels to the wire at room temperature, they
were baked on in a conventional manner at 260.degree.-480.degree.
C.
The heat shock was tested at 260.degree. C. for one-half hour at
20% prestretch and the results reported as the percent passed.
The following table shows the properties with 18-gauge copper wire
coated with the compositions of some of the examples described
above.
TABLE 1
__________________________________________________________________________
Wire Dissipa- Speed Mandrel Cut 260.degree. C. Burn tion Ft/ After
Thru Heat Shock Unidirect. Out Freon Factor Build Example Min.
Appear Snap .degree.C. 1X 2X 3X 4X Scrape (sec.) Resist.
(240.degree. C.) (mils)
__________________________________________________________________________
1(b) 45 3 2X 370 80-90-100-100 1000-1410 465 2.34 2.8 1(b) 50 3 1X
355 60-90-100-100 1100-1116 417 OK-OK 3.29 2.8 1(b) 55 3 1X 340
90-100-100-100 1100-1416 410 3.89 2.8 1(b) 60 3 1X 280
80-100-100-100 1166-1283 427 3.49 2.9 1(c) 50 4 1X 355
70-80-100-100 3.0 1(d) 50 4 1X 360 80-100-100-100 3.0 2(b) 50 3 1X
355 60-70-90-100 1250-1400 2.8 3(b) 50 3 1X 325 70-90-100-100 2.9
4(b) 50 3 1X 375 70-80-100-100 2.9 5(b) 45 3 1X 370 30-80-100-100
1000- 1000 2.9 6(b) 50 3 1X 360 40-80-100-100 1200-1416 3.0 7(b) 50
3 1X 360 50-80-90-100 1000-1500 3.0 8(b) 50 4 1X 320 10-80-90-100
3.0 8(c) 50 3 1X 295 50-80-100-100 1300-1466 2.9 9(b) 50 4 1X 350
50-90-100-100 1000-1250 2.9 9(c) 50 4 1X 290 10-80-100-100
1000-1216 2.9 10(b) 45 3 1X 365 10-70-90-100 1100-1450 475 3.62 3.0
13(b) 45 3 1X 385 30-90-100-100 1450-1450 459 3.51 2.9 14(b) 50 4
1X 355 50-80-90-100
__________________________________________________________________________
A. O. Smith Freon Test
This is a standard Freon test developed by A. O. Smith Co.
Procedure
Prepare a coil using 5 feet of coated wire. Wind the coil on a
mandrel (A. O. Smith specifications) to produce a 4-6% stretch on
the wire. For 18 gauge, this is a mandrel of 1-1/6 inch outer
diameter. Prebake coiled samples for two hours at 150.degree. C.
Remove and cool samples. Place in the Freon bomb and charge with
11/2 pounds Freon 22. Raise the bomb pressure by heating to 600 psi
and hold for six hours. Release pressure and immediately place
coils in an oven at 150.degree. C. for four hours. Remove coils and
check for blistering. The samples fail according to the following:
one large blister (in excess of wire diameter), two medium blisters
(from one-half to one wire diameter) or five small blisters (less
than half the wire diameter). A flexibility test is also run by
wrapping a length of wire on a 5X mandrel for 10 turns. The film
should not crack or peel. In addition, a twisted pair dielectric is
run on the samples that pass the previous tests.
The Composition of CA-43
CA-43, a product of Merichem Co., is a mixture of phenol and its
alkyl derivatives which has the following composition:
______________________________________ Component % by Weight
______________________________________ Phenol 6-8 O-cresol 9-10
M-cresol 15-20 P-cresol 8-11 O-Ethylphenol 1-3 M-Ethylphenol 9-11
P-Ethylphenol 3-5 2,6-Dimethylphenol 1 2,4-Dimethylphenol 11-17
2,5-Dimethylphenol 2,3-Dimethylphenol 10-13 3,5-Dimethylphenol
3,4-Dimethylphenol 5-8 2,4,6-Trimethylphenol 1
______________________________________ The formula of DID is
##STR1##
The polyester-imides of the present invention as indicated above
are usefu as a top coat for wires having a base coat of a polyester
or of a different polyester-imide. The polyester-imide products of
the present invention produce electrical conductor coatings having
extraordinarily high heat resistance.
Thermobonding and high heat resistance are mutually exclusive
properties. A polymer having a structure that will lend the polymer
softenable and bondable at temperatures such as 175.degree. C. will
not be able to withstand the performance rigors that the present
polyester-imide product withstands at 260.degree. C. Likewise, the
present product that is constructed to withstand 260.degree. C.
does not show the following bondability at 175.degree. C.
Experiments show that the present high, heat resistance polymer has
absolutely no bond strength and therefore undergoes no softening at
conditions used by the Keske to obtain bonding for their
polymers.
Moreover, the Keske and Czajka polyester-imide coatings are high
molecular weight thermoplastic compositions while the
polyester-imide coatings of the present invention are low molecular
weight thermosetting resins generally having an acid value between
0 and 10.
In following Table 2, the basecoat was Isonel 200
(tris-2-hydroxyethyl) isocyanurate-ethylene glycolterephthalate).
The wire construction contained four coats of the basecoat and two
coats of the respective topcoats, except for the last sample of the
new E.I. where there was only one topcoat layer and five Isonel 200
basecoat layers.
In Table 2 the topcoat referred to as AI is a polyamide-imide based
on the following formulation:
______________________________________ N--methylpyrrolidone (NMP)
80.4 grams Methylene diphenyl 25.0 grams diisocyanate (MDI) Amyl
alcohol 0.85 grams Trimellitic anhydride (TMA) 19.1 grams Solvesso
100 34.3 grams ______________________________________
These ingredients were cooked in conventional manner to produce an
enamel solution having a viscosity range of X 1/2-Y on the
Gardner-Holdt scale at a solids content of 26.5-28.5% based on a
two-gram sample that is baked for two hours in a forced air oven at
200.degree. C. The topcoat referred to as ISOMID is based on the
following formulation:
______________________________________ Polyesterimide resin at
82.5% solids 115.2 grams Cresylic Acid 177.4 grams Solvesso 100
112.8 grams Cresol formaldehyde resin at 40 .+-. 2% solids 15.1
grams Tetra Isopropyl Titanate 5.1 grams Isocyanate resin at 40
.+-. 2% solids, Mondur SH 32.8 grams 840 Silicone Resin 0.35 grams
______________________________________
The enamel solution was prepared in a conventional manner similar
to that used in the other examples to give an enamel having a
solids content of 26.5-28.5% and a viscosity of T 1/2-U 1/2 on the
Gardner-Holdt scale.
The topcoat referred to as "New EI" is the product described in
Example 1 of the patent application.
TABLE 2
__________________________________________________________________________
AL/ISONEL.RTM. ISOMID.RTM./ISONEL.RTM. New E.I./ISONEL.RTM.
__________________________________________________________________________
Pass 2/4 2/4 2/4 1/5 Heat Shock 260.degree. C. 80-80-90-100 0-0-0-0
10-50-70-80 10-20-40-60 220.degree. C. 80-100-100-100 0-0-0-0
30-40-70-100 70-80-90-100 200.degree. C. 80-100-100-100
60-80-90-100 80-100-100-100 50-80-90-100 Windability Pass 24 Pass
20 Pass 24 Pass 13 (1500V) A.O.Smith (Freon) Blister Two large
blisters Fails Few Blisters Fails Top coat lossened Flex Passes
Fails Passes Fails Diel(KV) 16.5 Fails 14.0 Fails After
__________________________________________________________________________
If there is compared the heat shock values at 200.degree. C., it
can be seen that all constructions are approximately equal in
performance. However, as the temperature of heat shocking is raised
to 220.degree. C., the construction with the ISOMID topcoat
completely fails the test. The new polyesterimide covered passes a
4X mandrel at 220.degree. C. At 220.degree. and 260.degree. C., it
does not quite measure up exactly to the heat shock resistance of
the AI/ISONEL construction, but offers acceptable performance at a
much lower price. AI/ISONEL construction is based on a
polyamideimide at approximately 22-28% solids using very expensive
N-methyl-pyrrolidone as a solvent. The new polyesterimide uses
conventional cresylic acid/hydrocarbon solvent blends which are
considerably cheaper, and employs considerably higher solids
levels.
In order to show the difference between the new polyester-imide
topcoat and that of the Keske patent, ISONEL 200 coated wire was
topcoated with the new polyester-imide and the coated wire was
wound, bonded at 175.degree. C. for 1 hour and tested for bond
strength. The results compared to that of Keske are set forth
below.
______________________________________ Bond Strength, lbs. at
Sample RT 175.degree. C. ______________________________________ New
E.I. 0 0 (of Example 1) Keske's E.I. 14.5 1.5 (U.S. Pat. No.
4,012,255, col. 8, line 49)
______________________________________
* * * * *